void main() {
    Scanner sc = new Scanner(System.in);
    System.out.println("请输入一个数字：");
    int num = sc.nextInt();
    if (num%3==0){
        System.out.println(num +"是三的倍数");
    }else {
        System.out.println(num +"不是三的倍数");
    }
}